1. Field Of The Invention
This invention relates to an electric windshield wiper apparatus for wiping a windshield or other window of, for example, an automobile. It more particularly relates to an electric windshield wiper having a concealed wiper unit housing a wiper blade in a concealed position during the time it is not being used, and in which it is possible to change-over the concealing operation.
2. Related Art Statement
An electric windshield wiping apparatus may have a concealed wiper unit for housing the wiper blade in a concealed position during periods of non-use. An example of such an apparatus has a design as shown in FIGS. 1 and 2.
That is, as shown in FIG. 1, an electric windshield wiping apparatus 100 has a circuit composed of a wiper motor 102 provided with an autostop switch 101, a change-over relay 103, and a wiper switch 104. The mechanical structure, shown in FIG. 2, mainly comprises a link coupling mechanism 105 connected to the wiper motor 102, a wiper arm 107 attached to a pivot 106 constituting a part of the link coupling mechanism 105 and a wiper blade 108 attached to the top portion of the wiper arm 107.
For instance, when the wiper switch 104 is shifted to a low-speed position LO, a circuit is established from a power source through a relay coil 103a in the change-over relay 103 and through a B terminal in the wiper switch 104 to ground. Completion of this circuit actuates the relay coil 103a, whereby relay contacts 103b and 103c on the change-over relay 103 contact with respective lower contacts. The closing of the contact 103b completes a circuit from the power source through the relay contact 103b on the change-over relay 103 through the M terminal on the wiper motor 102 to an L terminal in the wiper motor 102 which is connected to an L terminal in wiper switch 104 and thence to ground. Thereby, current is supplied to the wiper motor 102 to rotate the wiper motor 102 in the forward direction.
The rotation of the wiper motor 102 is converted into reciprocating movement of the wiper arm 107 through the link coupling mechanism 105. Thereby, the wiper blade 108 attached to the top portion of the wiper arm 137 is pushed to slide on a wiped surface 110 of a glass window 109 at a region extending from an upper turning position A to a lower turning position B.
Then, when the wiper switch 104 is changed to an OFF position at the end of use, the circuit extending from the change-over coil 103a through the wiper switch 104 to ground earth is interrupted. At the same time, when a P terminal in the autostop switch 101 is connected to its grounded E terminal (that is, the wiper blade 108 is positioned in a non-rest area on the wiped surface 110), the current flowing to the relay coil 103a passes through a diode 103d to the relay contact 103c and thence to the P terminal in the autostop switch 101. This current then passes the grounded E terminal in the autostop switch 101 to ground. This current thus continues the suction of relay contacts 103b and 103c by the relay coil 103b in the downward, contacting direction and the wiper motor 102 continues to rotate forwardly. Since the P terminal of the autostop switch 101 is connected to its B terminal in conjunction with rotation of the wiper motor 102 (that is, the wiper blade 108 reaches the lower turning position B), the current flowing to the relay coil 103a is then stopped to return the relay contacts 103b and 103c in the upper, non-contacting direction. As a result of this condition, the following circuit is established. The power source is connected to the B terminal in the autostop switch 101 and in this condition to the P terminal in the autostop switch 101. The circuit continues through the P terminal in the wiper switch 104, which in the OFF condition is connected to its L terminal. The circuit continues through the L terminal in the wiper motor 102 and then out through its M terminal to the change-over relay contact 103b and finally to ground. Thereby, a current having a polarity opposite to that of the above-described current is supplied to the wiper motor 102 to rotate reversely the wiper motor 102 in a direction opposite to the aforementioned rotation direction. Thus, the wiper blade 108 is further moved downward from the lower turning position B. That is, the wiper motor 102 is electrically controlled by the operation of the autostop switch 101 in accordance with the stop position of the wiper blade 108 so that the wiper blade 108 is stopped at a position lower than the lower turning position B, for example, at a housing position C beneath a hood 111.
Namely, when the wiper blade 108 reaches the housing position C by the reverse rotation of the wiper motor 102, the P terminal of the autostop switch 101 is connected to its E terminal in conjunction with rotation of the wiper motor 102. Then, a motor armature short-circuit is established from the M terminal on the wiper motor 102 through the relay contact 103b on the change-over relay 103 and through the E terminal of the autostop switch 101 and its P terminal and through the P terminal in the wiper switch 104 and its L terminal to the L terminal on the wiper motor 102, so that the wiper motor 102 is stopped immediately by the dynamic braking.
In the above electric windshield wiping apparatus, however, if the wiper blade 108 is at a housed state beneath the hood 111 during a snowfall, it cannot be smoothly operated due to the weight of snow lying on the concealed housing for the wiper blade 108 beneath the hood 111 or due to the freezing of the snow. For this reason, it is necessary to remove the snow or ice from the concealed housing before the operation of the wiper blade 108 so that the removal operation becomes troublesome.
When the wiper blade 108 is frozen to the vehicle body, if the wiper motor 102 is actuated, it is possible that the wiper motor is burned out or the rubber portion of the wiper blade 108 may be broken. Therefore, a method is generally used wherein the wiper arm 107 is raised up so as to break the contact of the wiper blade 108 with the vehicle body. However, in such a concealed wiping apparatus, the wiper arm 107 cannot be raised because it is housed beneath the hood 111. If the wiper arm 107 is broken due to the accumulated snow, it is difficult to replace the broken arm 107 with a new one and also difficult to perform the cleaning operation.
Therefore, there have been attempts to modify the concealing operation of the wiper blade 108 to guard against the above problem. For instance, one method reverses the attached position of a motor arm constituting a part of the link coupling mechanism 105 connected to the wiper motor 102 by 180.degree.. Another method replaces the described wiring of the wiper motor 102 with a previously arranged substitute wiring so as to not perform the concealing operation. Yet another method changes the position of the wiper arm 107 attached to the pivot 106. In these methods, the operation becomes difficult and the handling is poor. Furthermore, in certain cases the driver must get out of the passenger compartment to perform the required but troublesome operation.